Specific Enchants from villagers

Im trying to create a mod which adds a new villager profession called the enchanter, whos purpose is to sell enchanted books (as apposed to the current librarian), I have the profession set up and working, however I cant get any enchants to be applied to the books which are being sold. I assume this is something to do with nbt data, but i cant figure out how to add nbt data to a villager trade.

Any help is appreciated